JP3243942B2 - Pencil lead - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a baked pencil lead in which graphite, talc and / or mica are used in combination as a body material. The present invention relates to a pencil lead suitable for use as a pencil lead having a color tone, especially a pencil lead having a small diameter such as a lead for a mechanical pencil.

[0002]

2. Description of the Related Art In general, graphite is used as a body material in a pencil lead, but the gloss inherent in graphite crystals necessarily exists. In order to improve the luster peculiar to graphite, there has been known one using a body material other than graphite.

For example, as disclosed in Japanese Patent Publication No. Sho 42-7166, mica powder is used as a constitutional material, and as disclosed in JP-A-54-88423, as a constitutional material. Examples include talc.

[0004]

When mica or talc is used in combination with graphite as a constitutional material, it is possible to certainly reduce the gloss characteristic of graphite crystals, but another major problem arises here. . That is, when graphite is replaced with talc or the like, the amount of wear is reduced and the concentration is extremely reduced. When the amount of graphite is increased to prevent a decrease in concentration, the gloss specific to graphite becomes stronger, and in order to promote the wear of the entire fired core, when the bulk density of the fired core is reduced. Is extremely low in strength, and when used as a lead for mechanical pencils having a diameter of 0.9 mm or less, only those having no practical use can be obtained.

[0005] Accordingly, the present invention provides a method for manufacturing a semiconductor device having a diameter of 0.9 mm
Even when used as the following pencil lead, there is a sufficient amount of wear and concentration, and as a result, unlike the glossy handwriting of conventional graphite alone that maintains practical strength, a pencil with a pure black color tone It is intended to provide a core.

[0006]

By using talc or mica together with graphite as a constitutional material, the glossiness of the handwriting is reduced because the talc or the constitutional material present as abrasion powder of the pencil lead on the paper surface. It is considered that the carbide of the organic binder used as the binder is easily coated and present on the crystal surface of the mica. (In the case of graphite, delamination of the crystal easily occurs on the paper surface, and the gloss of the graphite crystal as it is appears in the handwriting.)

However, since the carbide is firmly coated on the surface of talc or mica in the pencil lead, the phenomenon of detachment of the filler from the carbide occurs as in a pencil lead using graphite alone. It is difficult, and as a result, it is considered that the amount of wear is small and the concentration is reduced. The talc and mica baked lead with the value of the desorption result of intensive studies to how to promote a specific surface area by CI method based on multi-layer adsorption theory baked lead from (pencil lead) (S1), a single BET based on molecular adsorption theory
When the ratio (S1 / S2) to the specific surface area value (S2) obtained by the method takes a value within a certain range, the detachment of talc or mica can be promoted, and it is extremely useful as a pencil lead. This led to the completion of the present invention.

[0008] That is, the present invention uses, as a main material, at least a mixture of graphite, talc and / or mica as an organic binder and a constitutional material, kneading, extrusion molding into a fine wire,
This is a fired pencil lead that has been subjected to a baking treatment, and has a specific surface area value (S1) based on the CI method based on the multilayer adsorption theory and a specific surface area value (S1) based on the BET method based on the single molecule adsorption theory.
The gist of the present invention is a pencil lead, wherein the ratio (S1 / S2) of 2) is 0.5 to 1.0.

The details will be described below. The specific surface area of the pencil lead of the present invention is measured using a fired core body after firing (before impregnating with the impregnating substance or after removing the impregnating substance), and the specific surface area is measured by a gas adsorption method. So, for example, the micro-Meretics Ore type specific surface area
Examples include a pore distribution measuring device 2100D, a flow type specific surface area measuring device Flowsorb 2300, and a high-speed specific surface area / pore distribution measuring device Asap 2000. The specific surface area (S1) based on the multi-layer adsorption theory and the specific surface area (S2) based on the single-molecule adsorption theory are obtained by calculation using nitrogen gas using these measuring devices. In the multi-layer adsorption theory, the Cranston-Inclay equation is used. Cylindrical model method (so-called CI
Method, and in the single molecule adsorption theory, it is determined according to the Brunauer-Emmett-Taylor method (the so-called BET method).

The specific surface area ratio (S
(1 / S2) is a value related to the shape of the fine pores in the fired core, and the smaller the value of (S1 / S2), the narrower the opening as a hole. That is, (S1 / S2)
In the range of 0.5 to 1.0, the shape of the pores is an ink bottle type having a narrower opening than the inside of the pores, and a structure in which fine slits are formed in talc or mica-coated carbide. It is thought that the abrasion of the mica is promoted, and the unevenness of the abrasion powder is increased and the blackness of the writing line is increased.

When the value of (S1 / S2) exceeds 1.0, the shape of the pores becomes a wedge type having a larger opening than the inside of the pores, and the bond between the talc and the mica coated carbide is strong. Because it is too much, talc and mica are less likely to be worn, and the concentration is reduced. On the other hand, when the value of (S1 / S2) is less than 0.5, there is a problem that the shape of the pores becomes too narrow compared to the inside of the pores, and it becomes difficult to impregnate the oil. Is not preferred. More specifically,
The value of specific surface area by monomolecular adsorption theory (S2) is not particularly limited, and reduced impregnation effect as much value for the specific surface area is small, also becomes small concentration-enhancing effects and blackness enhancing effect, if 50 m ² / G or more is more preferable.

The ratio of the specific surface area (S1 / S2) is 0.5
A specific manufacturing method for achieving a value of 1.0 is described. As the raw material, various methods can be considered depending on the combination of the type of the organic binder, the type of the pore-forming material, the heat treatment method, and the like. First, the organic binder is not particularly limited as long as a fired core having a target pore structure is obtained by combining a pore-forming material, and a thermoplastic resin,
Of these, chlorine-containing resins are most desirable from the viewpoint of pore formation.
The amount and type of the plasticizer used in combination with the thermoplastic resin used are also important points, and the heat treatment conditions during decomposition of the plasticizer and the temperature raising conditions during firing are also important points. For example, a thin line-shaped molded product obtained from a blended composition containing the same chlorine-containing resin and plasticizer is heat-treated at 200 ° C. or less for 10 hours, and further cooled to 1000 ° C. for about 5 hours in a nitrogen atmosphere.
The pore structure of the fired core is different between the case where the heat treatment is performed for 0 hours and the case where the heat treatment is performed to 300 ° C. for several hours and 1000 ° C. for several hours. Generally, the longer the time is, the lower the porosity and the bulk density are. The specific surface area tends to be high, and the specific surface area ratio (S1 / S2) also changes.

As a filler, graphite is an essential component for maintaining the strength of the pencil lead, but 90% to 1% of the total filler.
It is desirable to use 0%. Talc and mica used in combination with graphite can be conventionally known ones.Though talc whose surface is treated with a silane coupling agent, flaky talc by a wet pulverization method, and mica are only natural mica Instead, synthetic mica or the like can be used alone or in combination of two or more. In addition to the above organic binders and extenders, further, fillers such as inorganic fine powders such as carbon black used as needed, pore-forming materials such as depolymerizable resin powders and sublimable substances, solvents and the like. Use as appropriate. These are kneaded with a kneader, a three-roller, or the like, and then extruded to form a thin wire, and the ratio of the specific surface area (S1 / S2) of the fired core of the present invention is 0.5 to 1.0. A heat treatment method is applied. Furthermore,
If necessary, impregnate an oil such as spindle oil to obtain a pencil lead.

[0014]

【Example】

<Example 1> Vinyl chloride resin 30 parts by weight Talc (ND talc: manufactured by Nippon Talc Co., Ltd.) 25 parts by weight Graphite 25 parts by weight Dioctyl phthalate 10 parts by weight Dioctyl sebacate 2 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone (solvent) 30 parts by weight The above-mentioned material is kneaded with a kneader and a three-roll mill, then extruded into a fine wire, and heat-treated in the air from room temperature to 300 ° C. for about 10 hours. A baking treatment was performed in which the temperature was raised from room temperature to 700 ° C. in an atmosphere for about 3 hours and maintained at 700 ° C. for about 1 hour. After cooling, spindle oil was impregnated to obtain a 0.9 mm pencil lead.

Example 2 Example 1 was the same as Example 1 except that fit powder CT-35 (manufactured by Mika Yamaguchi Co., Ltd., particle size: 14.8 μm, wet process) was used as talc. To obtain a 0.9 mm pencil lead.

<Example 3> In Example 1, instead of talc, synthetic mica MK-300S (Corp Chemical Co., Ltd.)
And tricresyl phosphate in place of dioctyl sebacate used as a plasticizer, and the calcination is carried out in an inert atmosphere from room temperature to 800 ° C. for about 1 hour and 800 ° C. for about 30 minutes A pencil lead of 0.9 mm was obtained in the same manner as in Example 1 except that the lead was held.

<Example 4> In Example 2, 15 parts by weight of fit powder CT-35 and synthetic mica MK-30 were used.
Using 10 parts by weight of 0S, heat-treat from room temperature to 300 ° C. in air for about 15 hours, and raise the baking temperature from room temperature to 900 ° C. in about 5 hours in an inert atmosphere and 900 ° C. for about 2 hours A pencil lead of 0.9 mm was obtained in the same manner as in Example 2 except that the holding was performed.

<Example 5> In Example 1, talc treated with a silane coupling agent was used, and the amount of dioctyl sebacate used was changed from 2 parts by weight to 5 parts by weight. 0.9m
m was obtained.

Example 6 In Example 1, mica powder A-21 (manufactured by Mica Yamaguchi) was used in place of talc.
The baking treatment is performed at room temperature to 1000 ° C in an inert atmosphere for about 1
A 0.9 mm pencil lead was obtained in the same manner as in Example 1 except that the temperature was raised in 0 hour and kept at 1000 ° C. for about 2 hours.

Example 7 Same as Example 6 except that the amounts of mica powder A-21 and graphite were changed to 25 parts by weight, and 25 parts by weight to 4 parts by weight and 46 parts by weight, respectively. To obtain a 0.9 mm pencil lead.

Example 8 The same as Example 6 except that the amounts of mica powder A-21 and graphite were changed to 25 parts by weight and 25 parts by weight to 40 parts by weight and 10 parts by weight, respectively. To obtain a 0.9 mm pencil lead.

Comparative Example 1 The procedure of Example 1 was repeated except that the thin wire extruded was heat-treated at 180 ° C. for 10 hours, and then heat-treated to 800 ° C. in a nitrogen atmosphere for about 50 hours. In the same manner as described above, a pencil lead of 0.9 mm was obtained.

<Comparative Example 2> In Example 1, CTH # 125 manufactured by Nippon Talc Co., Ltd. (high whiteness talc obtained by calcination and pulverization treatment) was used as the talc, and the calcination treatment was carried out from room temperature to 1000 ° C. in an inert atmosphere. Was heated in about 5 hours and kept at 1000 ° C. for about 1 hour to obtain a 0.9 mm pencil lead in the same manner as in Example 1.

<Comparative Example 3> 31 parts by weight of vinyl chloride resin 35 parts by weight of talc (ND talc: manufactured by Nippon Talc Co., Ltd.) 25 parts by weight of graphite 10 parts by weight of carbon black 17 parts by weight of magnesium stearate 30 parts by weight of methyl ethyl ketone (solvent) 30 parts by weight Part After kneading the above-mentioned materials as a compound and sufficiently kneading with a kneader and three rolls, extruding into a fine wire form, heating in air from room temperature to 300 ° C. for about 30 hours, and further, in an inert atmosphere. The temperature was raised from room temperature to 950 ° C. in about 3 hours, and a baking treatment was performed at 950 ° C. for about 1 hour. After cooling, spindle oil was impregnated to obtain a 0.9 mm pencil lead.

<Comparative Example 4> Coal tar pitch 50 parts by weight Talc (ND talc: manufactured by Nippon Talc Co., Ltd.) 35 parts by weight Graphite 25 parts by weight Carbon black 10 parts by weight A kneader and a three-roll mill using the above materials as a compound After sufficiently kneading, the mixture is extruded into a thin wire, and is heated from room temperature to 500 ° C. in an inert atmosphere for about 10 hours, and from 500 ° C. to 90 ° C.
The temperature was raised to 0 ° C. in 4 hours, and a baking treatment was performed at 900 ° C. for 1 hour. After cooling, impregnate with spindle oil.
A 9 mm pencil lead was obtained.

With respect to the material obtained in each of the above examples, the calcined core body before the oil immersion treatment was measured using a nitrogen gas with an Oer type specific surface area / pore distribution measuring device 2100D manufactured by Micromeritics Co., Ltd. The specific surface area (S1) based on the multilayer adsorption theory (CI method) and the specific surface area (S2) based on the single molecule adsorption theory (BET method) are obtained, and the ratio (S1 / 1)
S2) was calculated. Furthermore, the concentration of the oil-treated pencil lead was measured according to JIS S6005.
(The density has a correlation with the amount of abrasion.) Further, in order to determine the color tone (blackness) of the writing line, a Kent paper is surface-coated with a load of about 600 g (thickness such that even a pencil lead having a different density has the same abrasion amount). Painted) on the SM color computer SM-5
The Y value was measured using Model 1S-2B (manufactured by Suga Test Instruments Co., Ltd.). (The lower the Y value, the higher the sensory blackness.) The results are shown in Table 1.

[0027]

[Table 1] * 1 indicates S1 (m ² / g), * 2 indicates S2 (m ² / g), * 3 indicates S1 / S2, * 4 indicates concentration (D), and * 5 indicates Y value.

[0028]

According to the present invention, even when graphite and talc and / or mica are used in combination, it is possible to obtain a practical pencil lead having a large amount of wear, a high concentration and a dark handwriting.

Claims (1)

(57) [Claims] 1. A fired pencil formed by kneading, extruding into a fine wire shape, and then firing, using at least a material obtained by combining graphite, talc and / or mica as an organic binder and a constitutional material. A core, based on multilayer adsorption theory, C
The ratio (S1 / 1) of the specific surface area value (S1) by the I method and the specific surface area value (S2) by the BET method based on the single molecule adsorption theory
A pencil lead, wherein S2) is from 0.5 to 1.0.